A DMSA (DiMercaptoSuccinic Acid) scan uses radioactive chemicals to create special pictures of the kidneys. These pictures help doctors assess how well the kidneys are working. DMSA travels through the body joined to a radioactive chemical. It builds up in the kidneys. Pictures of the kidneys are then taken using a "gamma camera" which can measure the radioactive emissions from the material collected in your kidneys. Unlike other forms of measurements on urine that's already left the body, a DMSA scan can show how one kidney is performing compared to the other. The radioactive material will then work its way out of your system over the next 24hrs.
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| Gamma camera at Harefield hospital |
The above photos, taken with kind permission of the radiology department staff, are of the actual gamma camera at Harefield hospital that took my images. The display screen in the left-hand photo is positioned so you can see it during the scan. The right-hand photo shows the camera positioned at 45 degrees.
Taking a DMSA scan
A DMSA scan essentially has two phases: injecting small amount of radioactive tracer, and then, after 3 hours, once the tracer has worked its way round your body to your kidneys, the scan itself.
The injection is quick and simple, into a vein in the arm. You shouldn't feel the effect. No stinging. No fuzzy warm feeling. No muscle ache. Then, you can leave the Nuclear Medicine department for a while. Take a walk. Have lunch or afternoon snack at Harefield's cafe. The only constraint is that, if you need the loo, they ask you to use a dedicated facility within the Nuclear Medicine department, as your pee will now be radioactive. Not in a big way, but over time, with lots of patients, waste products need to be correctly managed, rather than just left to irradiate the town of Harefield and its environs.
The second phase is the scan itself. Simply remove heavy clothing and lie on the bed of the scanner. It might look like a CT machine, but, the CT "doughnut" bit itself isn't used. Attached to the machine, are a pair of "gamma cameras", facing each other. You are slotted between them; initially one above you, and one below, like a sausage in a bun. The cameras are then positioned as close to your body as possible, to provide a sharp image. When the scan itself begins, it's important to keep still - or you'll just create a fuzzy image. The first scan takes around 10 minutes, with the monitor positioned so you can see an on-screen timer tick away. Two more images are then taken with the cameras rotated to "10 to 4" and "10 past 8" positions, to collect transverse views. These scans are slightly quicker.
After the scan
Following your scan, you can eat and drink as normal. You may go anywhere you like. You may drive - assuming you were allowed to do that before the scan! But, try to avoid long periods of close contact with young children for the rest of the day, as you'll still be emitting radiation. For example, it's best not to snuggle on the sofa with an infant to watch Disney's latest movie that day. The results of the scan will be sent directly to the requesting consultant within a week.
Private patients
A DMSA scan is not a routine procedure for kidney cancer patients on the NHS. The diagnosis can often be confirmed with a CT scan. However, it may be useful to know how well each kidney is performing individually. Normally, kidneys split the combined workload 50:50, +/- 2%. ie. Anything around 48% / 52% is considered normal. In my case, the pre-op DMSA scan reported 46% (healthy kidney) vs 54% (kidney with tumour). Such information adds weight to the case for partial, versus full, nephrectomy; as losing the kidney that does most of the work would create even more strain on the kidney that remains.
A DMSA scan can be booked at Harefield Hospital, as a private patient, for £267 (Nov 2013). You might consider your kidney to be worth it.
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